A technique used to rewrite a quadratic function in standard form to vertex form is

The vertex form of a quadratic function is given by
                                      [tex]f(x)=a(x-h)^{2}+k, [/tex]
where (h,k) is the vertex of parabola. In some literatures, the standard form of the quadratic equation is written as 
                                     [tex]f(x)=a x^{2} +bx+c[/tex] 
Therefore, in order to avoid the confusion, the first equation is taken as a vertex form. When the standard form is converted into the vertex form, the process is called completing the square.